#include<bits/stdc++.h>
using namespace std;
#define rep(i,j,k) for(int i=j;i<=k;++i)
#define per(i,j,k) for(int i=j;i>=k;--i)
#define IOS {cin.tie(0);cout.tie(0);ios::sync_with_stdio(0);}
#define int long long
#define ll long long
#define P pair<int,int>
#define vi vector<int>
#define double long double
#define db double
const int N=1e5+5,inf=1e9+7;
int n,m,fl;
P a[N],b[N];
db s1[N],s2[N],mi; //len,mid*len
db lb[N];
db f1(int l1,int r1,int l2,int r2){  //l1>r2
    return ((l1+r1)/2.0-(l2+r2)/2.0)*(r1-l1)*(r2-l2);
}
db p3(db x){return x*x*x/3;}
db cal(int i,int j){
    if(fl){
        db l1=a[i].first,r1=a[i].second,l2=b[j].first;
        return (l2-l1)*(-l1+l2)/2+(r1-l2)*(r1-l2)/2;
    }
    db res=0;
    P ta=a[i],tb=b[j];
    if(ta.first<tb.first)swap(ta,tb);
    if(tb.second<ta.second){
        res+=f1(ta.first,ta.second,tb.first,ta.first);
        res+=f1(tb.second,ta.second,ta.first,tb.second);
        res+=p3(tb.second-ta.first);
    }
    else{
        res=f1(ta.first,ta.second,tb.first,ta.first)+f1(ta.second,tb.second,ta.first,ta.second)+p3(ta.second-ta.first);
    }
    return res;
}
bool crs(int i,int j){
    return (!(b[j].second<=a[i].first)) && (!(b[j].first>=a[i].second));
}
signed main(){
    IOS
    cout<<fixed<<setprecision(15);
    // cout<<2e9/3<<endl;
    cin>>n>>m;
    ll sa=0,sb=0;
    rep(i,1,n){
        cin>>a[i].first>>a[i].second; sa+=a[i].second-a[i].first;
    }
    rep(i,1,m){
        cin>>b[i].first>>b[i].second; sb+=b[i].second-b[i].first;
    }
    // if(a[2].first==-829)assert(sb);
    b[m+1].first=inf; b[0]={-inf,-inf};
    if(sa==0 && sb==0){
        int L=0; db ans=0;
        sort(a+1,a+n+1); sort(b+1,b+m+1);
        rep(i,1,m)s2[i]=s2[i-1]+b[i].first; //先sort再预处理!!!!!!!!!
        // rep(i,1,n){
        //     rep(j,1,m)ans+=abs(a[i].first-b[j].first);
        // }
        rep(i,1,n){
            while(b[L+1].first<=a[i].first)++L;
            ans+=1ll*a[i].first*L-s2[L] + s2[m]-s2[L]-1ll*a[i].first*(m-L);
        }
        cout<<ans/(1.0*n*m);
        return 0;
    }
    if(sa==0){
        swap(n,m); swap(a,b); swap(sa,sb); 
    }
    sort(a+1,a+n+1); sort(b+1,b+m+1);
    if(sb!=0){
        rep(i,1,m)lb[i]=b[i].second-b[i].first;
    }
    else{
        sb=m; fl=1;
        rep(i,1,m)lb[i]=1;
    }
    rep(i,1,m){
        s1[i]=s1[i-1]+lb[i];
        s2[i]=s2[i-1]+lb[i]*(b[i].second+b[i].first+0.0)/2;
    }
    int L=0;
    db res=0;
    b[m+1].first=inf; b[0]={-inf,-inf};
    // cout<<n<<endl;
    // rep(i,1,n)cout<<a[i].first<<" "<<a[i].second<<endl;
    // rep(i,1,m)cout<<b[i].first<<" "<<b[i].second<<endl;
    rep(i,1,n){
        while(b[L+1].first<=a[i].first)++L;
        // cout<<L<<endl;
        int l;
        if(crs(i,L))l=L; else l=L+1;
        int r=l-1;
        while( crs(i,r+1) )++r;
        // cout<<l<<" "<<r<<endl; 
        // cout<<s2[m]-s2[r]<<" "<<s1[m]-s1[r]<<endl;
        mi=(a[i].first+a[i].second)/2.0;
        res+=( mi*s1[l-1] - s2[l-1])*(a[i].second-a[i].first);
        res+=(s2[m]-s2[r]- mi*(s1[m]-s1[r]) ) *(a[i].second-a[i].first);
        // cout<<res<<endl;
        rep(j,l,r)res+=cal(i,j);
        // cout<<res<<endl;
    }
    // cout<<res<<endl;
    cout<<res/(1.0*sa*sb);
}
/*
4 4
1 1
3 3 
7 7
9 9
0 2
2 5
6 8
10 11

144/32 != 147/32

3 1
5 5
9 9
7 7 
1 10

4 4
1 1
7 7 
3 3
9 9
3 3
4 4
7 7
8 8

2 3
3 6
7 9
1 4
5 8
9 10
2.771428

1 1
0 2
1 1

2 2
3 6
7 7
1 4
5 7

2 2
0 1
2 4
1 1
3 3
13/6

4 3
1 1
2 2
3 3
4 4
1 1
3 3
5 5
1.6666667

*/